Ordinary fusel oil is of value chiefly on account of the amyl alcohol which it contains, and it is, or should be, appraised commercially on this basis.

An approximate method of estimating the amyl alcohol was devised by Allen. It consists in agitating the sample in a graduated tube with an equal volume of benzene (or petroleum spirit). Sufficient water is then added to cause the benzene to separate. The increase in the volume of the benzene layer gives approximately the volume of amyl alcohol in the sample.

It is obvious that this is only a rough method, which would serve fairly well if amyl alcohol were practically the only higher alcohol present, but which would include as amyl most of the butyl and propyl alcohols in the sample.

G. Heinzelman2 has described the method used at the Institut fur Garungsgewerbe, Berlin, for determining the proportion of amyl alcohols in fusel oils. It consists in ascertaining by fractional distillation the proportion of distillate boiling at 127-131°. A special form of fractionating column is employed; a figure of this is appended.

1 "Industrial Alcohol," p. 176.

2 Zeitsch. Spiritusind., 1912, 35, 612; J. Soc. Chem. Ind.t 1912, 31, 1142.

Four fractions are collected: (a) up to 90°, (b) between 90° and 115°, (c) between 115° and 127°, and (d) between 127° and 131°.

Fraction (a) contains ethyl alcohol, some fusel oil, and water. It is distilled from a water-bath through the fractionating column as long as ethyl alcohol passes over. The residue is removed to a separator, saturated with common salt, and the fusel oil portion which separates is obtained by running off the saline solution.

Fraction (b) is also treated with salt, and the fusel oil portion separated in the same way. This is. mixed with that obtained from (a), and re-fractionated. When the thermometer indicates 112° fraction (c) is added, and the distillation continued, the portion passing over at 127° and above being collected separately. Its amount, added to that of fraction (d), gives the total yield of amyl alcohols.

The quantity of fusel oil taken for distillation is 1,500 c.c. In an example given, fraction (a) amounted to 540 c.c, (b) to 420 c.c., (c) to 45 c.c., and (d) to 475 c.c. From the refractionation of (a), (b), and (c), 175 c.c. were obtained distilling above 127°. The total yield of amyl alcohols was therefore 650 c.c., or 433 per cent. by volume.